There has been extensive research in the area of gastric retentive drug delivery systems and dosage forms. These systems and dosage forms are particularly useful for the delivery of drugs that:                (1) have a “narrow absorption window” in the gastrointestinal tract, for example, drugs that are preferentially absorbed in the duodenum and/or jejunum over ileum and/or colon, or have better solubility in upper parts of the gastrointestinal tract (GI);        (2) are intended for local treatment of proximal parts of the gastrointestinal tract (stomach and/or duodenum); and/or        (3) degrade in the colon or in the intestines, etc.        
Gastric retentive drug delivery systems or dosage forms have focused research in three areas of technology: namely, floating systems; systems with expanding geometry through swelling or unfolding; and bioadhesive systems.
The general concept of the expandable gastroretentive systems and dosage forms is that the system or dosage form starts in a condition or configuration suitable for swallowing. The system or dosage form then expands in the stomach to prevent gastric emptying. Eventually, the system or dosage form reduces in size to pass through the pylorus or disintegrates. Some of the original formulations with this approach are known from the veterinary world. For example, U.S. Pat. No. 3,844,285 discloses the concept of a pill that can be swallowed with wings taped down that eventually expand once water-degradable tape disintegrates. Such veterinary gastroretentive devices and formulations are sold under the tradenames Captec® and Ivomec® SR Bolus. In the area of commercialized animal products, Paratect Flex® bolus is a trilaminate sheet with a central polymeric matrix and drug load which is rolled up and held by a piece of water-soluble adhesive tape in the form of a cylindrical pill.
In the area of human oral application, U.S. Pat. No. 5,002,772 discloses a device with a plurality of compressible retention arms attached to a controlled release device which, in the expanded configuration, resists gastrointestinal transit. U.S. Pat. Nos. 4,735,804 and 4,767,627 disclose a series of substantially planar geometric shapes, e.g., a tetrahedron formed of a bioerodible polymer that may be compressed and collapsed for oral administration. U.S. Pat. No. 8,298,574 discloses an “Accordion pill”, a sheet with a length of more than 20 mm, folded like an accordion and placed in a capsule.
There have been many challenges in designing gastric retentive dosage forms relating to ability to scale up/manufacture/assemble, drug loading capacity, retention during fasted state, the inclusion of an emergency release mechanism to expel the delivery system or dosage form in an emergency situation, using pharmaceutically acceptable ingredients etc. Improvements concerning any one of these challenges would provide a significant contribution to the area of gastric retentive drug delivery systems and dosage forms.